As environmentally-friendly vehicles, a hybrid vehicle and an electric vehicle are vehicles using, as a power source, a direct-current power supply, an inverter and a motor driven by the inverter in addition to a conventional engine. Specifically, a power source is obtained by driving an engine, as well as converting a direct-current voltage from a direct-current power supply into an alternating-current voltage by an inverter and rotating a motor by the converted alternating-current voltage. Additionally, an electric vehicle is a vehicle which uses, as a power source, a direct-current power supply, an inverter, and a motor driven by the inverter.
This inverter is provided with a capacitor for smoothing direct-current power from the direct-current power supply. The inverter needs to be provided with a discharging circuit function of discharging charges remaining in the capacitor after the inverter stops. The inverter is also provided with a step-up converter for stepping up a direct-current voltage from the direct-current power supply.
PTL 1 discloses that in a control device 30, residual charges of a capacitor C1 connected between a step-up converter and a direct-current power supply are consumed by step-up operation by the step-up converter and residual charges of a capacitor C2 connected between the step-up converter and an inverter circuit are consumed by step-down operation by the step-up converter.
However, it demanded to further reduce a discharging time required for discharging residual charges of a capacitor.